I propose to study the regulation of the dopa decarboxylase gene of Drosophila melanogaster. To begin these investigations, I have isolated the DNA containing the DDC genomic coding sequences. This has been accomplished utilizing recombinant DNA technology. In the proposed experiments, I will use this cloned DNA 1) as a specific probe to detect RNA transcripts made from this region in vivo, and 2) to study the DNA sequences within and surrounding the coding sequence. Since the enzyme activity of DDC can be easily measured, I will be able to make correlations between levels of DDC RNA and levels of enzyme activity. By examining levels and sizes of RNA molecules at various stages of the life cycle, I should be able to get a general picture of the regulatory mechanisms. By comparing amounts of pulsed labeled RNA with steady state levels, it should become clear whether the primary regulation is transcriptional or post transcriptional. I will also use in vitro organ culture of imaginal discs. This preparation has the potential for allowing the study of DDC induction in a relatively homogeneous cell population. Several strains have been isolated with mutations in the DDC region that appear to affect coordinately levels of DDC and of a related gene closely linked to DDC. By cloning DNA from the mutant strains and determining the sequences which are altered, I may be able to learn the functional significance of the sequences involved.